Control device for incandescent lamp cinematographic apparatus



Dec. 31, 1935. K. ROSENBERG 2,026,437

CONTROL DEVICE FOR INCANDESCENT LAMP CINEMATOGRAPHIC APPARATUS Filed March 22, 1934 WWW X FIG. 7.

PER/006' 0F /LL UM //VA 770/V OF CELL 1.

OF JW/ TC// 7 x Z pip/00S OFCL 051mb: OF JW/ TC 8 3 PfR/0OS 0F c1: 050/?5 OF SW/T'CH 10 Patented Dec. 31, 1935 UNITED STATES PATENT pm;

CONTROL DEVICE FOR INCANDESCENT LAMP cmnm'rooaarmc APPARATUS Kurt Rosenberg, Berlin, Germany, assignor to Reklamaktiebolaget Epok, Stockholm, Sweden, a corporation of Sweden Application March 22, 1934, Serial No. 716,878

Germany March 14, 1933 Up to now holding coils were provided for the relays which, being arranged in the electrical circuit of the lamps, were put in circuit by the relay, upon the current for the lamp being switched on, and held the relay armature in its attracted position, a circuit-breaker, arranged in the main circuit, interrupting the current for the lamps aiter each alternating film picture, thus causing the relay armature to fall off. The number of changes in the film picture, taking place in the projection apparatus per time unit, had to correspond to the number of interruptions (about 24 per second). This number, however, does not in all cases correspond to the .real change of the phases in a film to be transmitted. Ii for instance, a film is transmitted, showing for a certain period of time a picture without a movement, then the relays controlling the various picture points, continually have to carry out their switching action in correspondence with the changes taking place in the film picture, i. c. after each and every single film picture, in spite of the fact that it would be suflicient to carry out only one switching-on and one switchingout operation covering the entire period oi time during which a portion or the film picture is transmitted which does not show ,a change.

The present invention realizes this task by the arrangement of holding coils in a separate cir cult, and by providing an adequate successive arrangement in the interruption operations taking place within the different circuits. The idea of invention is explained by the drawing:

Figure l is a relay arrangement with holding coil, in which the relay is provided with two connecting contacts.

Figure 2 is a relay arrangement with one connecting and one disconnecting contact.

Figure 3 is the time graph of the single interruptlon operations.

In the first figure I is the cell, 2 the source The switching, operations in the different circuits are the following:

The film is projected on to the photo-cell screen. It a cell is exposed to light, falling on it,

the relay armature is attracted accordingly, 5

whereby the circuit for the holding coil is closed by means of a pair 01' contacts 6, the relay armature thus being kept in its position by the action of the holding coil attracting it. The circuitbreaker 1 arranged in the circuit actuating the holding coil 4, acting synchronously and being in phase with the film transportation device, as will be explained below in detail, is to be considered to have its closed position.

Upon the relay armature being attracted, the 5 pair of contacts 8, arranged in the circuit for the lamps is also closed, whereas the main circuit-breaker II), also acting synchronously and in phase with the film transportation is opened,

and is closed only after the relay armature having been attracted, the pair of contacts 8 thus being brought into its closed position when the circuit is dead.

The holding current having once been closed by the action of the pair of contacts 6, a discontinuance of the cell-current in case-oi the cells no longer being exposed to light, as takes place for-instance in the dark intervals during the transportation of the film reel-which current otherwise would have an influence on the relay 3o relay coil, 4 the holding coil, 5 the source of current for the holding coil, 6 the contact closing the circuit for the holding coil, I a circuit-breaker, 8 the contact switching on the current for the lamps, 9 the source of current for the lamps, III

a second circuit-breaker, and II the incandescent lamp.

The circuit for the lamps is closed, by way of the contact 8, when the relay armature is in its dead position, whereas the circuit for the holding,

,coil is closed, by way of the contact 6, when the relay armature takes its attracted position. The

, film picture being projected is, so to say, the negative of the picture appearing on the lamp screen, in view of the fact that a darkening of the photoelectric-cells causes the relay armature to fall :35

' g2 .aoeensr oi, the lamps thus being switched on, whereas light falling on to the cells causes the relay armature to'be attracted, the lamps thus being switched off. The interruptions within the vari- 6 ous electric circuits by means of the interrupters l and ID are otherwise the same as above, and as illustrated b Figure '1. j I

The sequence of the stages ofoperation's taking place in the difierent circuits (in the relay coils, 10 in the holding coils and in the electrical circuit for the lamps) is explained more fully by the graph, Figure 3. (The lengths of the single sections do not represent any definite numerical values, as the latter can well be neglected, as faras the principle underlying the inventive idea concerned.)

a Line I represents the chronological sequence of the relay emanating from the film projecting apparatus. The intervals interrupting line I represent the periods of darkness caused by the rotating diaphragm when concealing the film transportation movement. At the same time line i represents .the photo-electric current i passing through the relay coil, as 'the cell supplies cur 25 rent'when exposed to light.

By line i it is shown that a relay influenced by the photo-electric current would continuously 'switch on and. oif in correspondence with the darkening of the cells, because the relay current M would be continually subject to interruptions corresponding to the periods of darkness.

As explained above the circuit of a holding coil is being closed uponthe armature of the relay being attracted; This current, however, must be period- 35 ically interrupted short periods of time,

in order to free the relay for a new light-electric operation-.- These interruptions, as shown by line 2 in the graph, are so.arranged as to coincide with the v periods when the cell is exposed to light, i.-e.

those periods when the relay coil is continuously supplied with; current. As long as the cell is continuously exposed to the influence of light, the relay armature therefore will continue to be kept 45 in its attracted position, because, as soon as during thexperiods of darkness the current for the cells (circuit for the relay) is cut ofi, the holding coil will take over the function of attracting the relay armature. On the other hand, in case of vthe current actuating the'holding coil being cut oif in consequence of the periodical interruptions, the relay coil is influenced by the photo-electric current the armature thus also being kept in its attractive position. The relay armature thus will continue to be permanently attracted upon the cell corresponding to its relay being exposed to the influence of light.- (See Figure 3, line 3 of the graph.)

60 It is possible for the relay armature, after having been attracted, to disengage itself as soon as both the current for the photo-cells and the current for the holding coil have been interrupted. This happens in the moment when the vnt tu ting-the holding coil has been interrupted, sothat the attracted relay armature v, re-adopts its dead position, thereby disconnecting he circuit of its holding coils by means of its pair "contacts. The armature of the relay can be 'ttr'acted again as soon as thecell corresponding o itis exposed to light, whereupon the circuit of be holding 'coil is closed again said armature will 'held'gin its'position thereafter by the photo whole period of transmission, the wear and tear 1o of the relay contacts thereby being reduced to a minimum, resulting in an increase of the working reliability of the whole plant. I

The possibility is already known of breaking the current for the lamps to be switched-on and 15 switched-0E, respectively, by the contacts of the relays, just in the moment when the contacts of the relays are moving, a formation of sparks on the contacts thereby being prevented.

As shown above, the moments when the relay armatures are moving, coincide firstly with the moment when the current for the holding coil is disconnected, and again with the moment when the cell commences to be exposed to the influence of light, he. the moment immediately after the film reel in the projector has moved on, when the rotating diaphragm lets pass theray of light. In both these moments the circuit for the lamps must be broken for a short time, because just these moments ofier a possibility for the armature of the relay to be attracted.

- Line ii of the graph shows the manner in which the interruptions of the circuit for the lamps are 7 distributed. The illustration shows that the interruptions'in the circuit for the lamps amount to twice the amount of interruptions in the cir- I cuit for the holding coil. This is another ad vantage, because by an increase in the number of interruptions the troublesome flickering, if any, of the picture to be transmitted will be reduced or abolished.

- The improvement implied in the present control devices, as compared with those known up to now, is that the relays are put into operation .only' in'case of the film picture to be transmitted i5 Means for reproducing on a s'creen composed l of incandescent lamps, film pictures projected on a bank of photo-cells comprising a cell current source and a relay coil connected in series with .each photo-cell; a holdingcircuit and a relay holding coil, a holding coil current source, a circuit breaker'and a relay contact connected in series in said holding circuit; a lamp circuit and a lamp current source, a second circuit breaker and a second relay contact connected in series in said lamp circuit, the two relay contacts being operable by either of said coils, said relay coil being controlled by-said photo-cell whereby, during periods of illumination of saidcell, the relay contacts are closed, means for synchronizing the operation of the two circuit breakers with the film 

